Reese and Vince Fight On Set

Looks like there's nothing funny on the set of the new comedy film "Four Christmases" as its stars, Reese Witherspoon and Vince Vaughn, are not getting along.

Apparently, the pair has begun to argue on the set because of their acting methods differences. Reports say that Witherspoon does not like the actor's laid-back approach to acting.

"Vince rolls onto set in the morning looking like he just came in from a night out, while Reese will arrive early looking camera-ready," a source was quoted. "Then Reese tries to force Vince to into blocking out each scene and running through their lines as Vince tries to convince her that he's an ad-libber and wants to play around and see where the scene goes."

"She's a one-take perfectionist and Vince likes to try it a few different ways. Sometimes Vince will be standing behind her and he has this look on his face that he just wants to kills her!"

The two were said to be pals before the shoot as Witherspoon was trying to get Vaughn and his ex, Jennifer Aniston, back together. She had appeared in Aniston's then TV comedy series, Friends, as her little sister.